Device for preparing hot water, in particular for domestic applications

ABSTRACT

A device which is used for preparing hot water, in particular for domestic applications, by recovering heat from waste water, preferably waste water from a sink and/or a dishwasher or washing machine includes a heat pump having an evaporator and a condenser, and a waste water container which collects the waste water. The waste water container is placed in thermal contact with the evaporator and constructed as a cylindrical hollow body with a waste water inlet and a waste water outlet. A hot water reservoir is in thermal contact with the condenser. Accommodated in the hollow body of the waste water container is an agitating apparatus, and a valve is provided at the waste water outlet to cut a flow of waste water through the waste water outlet.

The invention relates to a device for preparing hot water, in particular for domestic applications, by recovering heat from waste water, preferably waste water from a sink and/or a dishwasher or washing machine, by means of a heat pump, in particular a compression heat pump, having a waste water container which collects the waste water, and a hot water reservoir, wherein the evaporator of the heat pump is in thermal contact with the waste water container and the condenser of the heat pump is in thermal contact with the hot water reservoir.

Devices of said type permit the thermal energy present in the waste water of domestic applications to be extracted before said waste water is discharged into the drain system. A device of said type is known from EP 0 088 055 A1, the device described there containing a waste water collection container which permits the temporary storage of the hot water, and in addition a heat pump which extracts the energy from the hot waste water and supplies it to a container which serves for storing the hot water.

Similar devices are described in DE 30 06 119 A1, DE 28 01 638 A1 and DE 26 25 157 A1.

In order to enable the thermal energy contained in the waste water to be extracted therefrom to a sufficient extent it is necessary to store the waste water in the waste water container for a relatively long period of time. However, this means that the contaminants or particles contained in the waste water are able to collect as a deposit on the wall, in particular in the lower region of the waste water container, as a result of which not only is a coating produced which becomes difficult to remove over the course of time, but the coating also forms a heat-insulating layer besides, thereby making it more difficult for heat to be transferred to the evaporator of the heat pump which typically is arranged on the external wall of the waste water container.

The object underlying the invention is to improve a device of the type cited in the introduction to the effect that deposits of dirt particles in the waste water container are avoided and consequently an optimal transfer of heat through the wall of the waste water container is ensured.

This object is achieved according to the invention in that the waste water container is provided with an agitating apparatus.

The advantage achieved by means of the invention essentially consists in the fact that the agitating apparatus keeps the waste water in the waste water container in motion so that deposits cannot accumulate on the wall of the waste water container or at most can accumulate only to a minor extent. In particular this renders any anti-dirt coatings on the internal wall superfluous. Furthermore, the agitating apparatus ensures the water is circulated in the waste water container, thereby enabling the thermal energy contained in the waste water to be extracted more quickly, with the result that a heat gradient from the center of the waste water container toward the edge is avoided. In addition, the agitating apparatus can simultaneously perform a pumping or conveying function for the waste water.

In a preferred embodiment variant of the invention the waste water container is implemented as a cylindrical hollow body having a waste water inlet and a waste water outlet, the agitating apparatus being formed by a driven shaft running coaxially in the waste water container and having agitating elements arranged thereon.

In this variant the agitating elements can be designed in any suitable form, for example also as agitating blades; in this case it has also proved advantageous within the scope of the invention if the agitating elements are embodied as a worm, since a conveying function is fulfilled by this means.

Advantageously, the agitating elements can in this case also be structured in such a way that they form a closure means for the waste water.

Alternatively or in addition, a valve can furthermore be provided at the waste water outlet as a closure means for the waste water. Said valve remains closed at first until the waste water has cooled down to a predetermined lower temperature value.

In order to avoid deposits of dirt particles to the greatest possible extent it is beneficial to embody the agitating elements in such a way that they are in contact with the wall surface of the waste water container or are disposed facing it with a slight gap.

In a particularly simple embodiment the drive shaft can be driven by a motor.

In order to be able nonetheless to clean the waste water container easily, such a cleaning operation being advisable at relatively long time intervals, it is provided within the scope of the invention for the drive shaft together with the agitating elements and the motor to be embodied as a structural unit which can be easily removed from the waste water container for cleaning purposes.

It has furthermore proved beneficial if the waste water container is arranged inclined at an angle with a fall toward the waste water outlet.

This also facilitates the conveyance of the particles contained in the waste water toward the waste water outlet.

In order to enable a first preheating of the fresh water flowing into the hot water reservoir to be performed, the invention makes provision for a preliminary heat exchanger for the fresh water to be provided on the waste water container. Said preliminary heat exchanger is beneficially formed by a coiled pipe running in a spiral shape around the housing of the waste water container.

In order to achieve an effective and maximally homogeneous extraction of heat from the waste water container it is furthermore advisable to arrange the coiled pipe of the preliminary heat exchanger and the coiled pipe of the evaporator in the manner of a common bifilar winding.

It has also proved advantageous if the inlet of the hot water container is provided in the latter's lower region and is connected to the outlet of the preliminary heat exchanger. In this way the hot water can collect in the upper region of the hot water container without being mixed with the replenishing fresh water, such that the hot water is ready to be drawn off in the upper region. For this reason it is additionally advisable for the condenser and the hot water outlet to be arranged in the upper region of the hot water container.

Finally, it is advisable, in order to avoid heat losses, for the waste water container, the heat pump and the hot water reservoir to be enclosed by a common heat-insulating means. In this way the entire device also forms a unit which can replace the otherwise customary electric boiler under the sink.

The invention is explained in more detail below with reference to an exemplary embodiment illustrated in the drawing; the single FIGURE is a schematic diagram showing the device for recovering heat from waste water.

The device depicted in the drawing is provided in particular for domestic applications in order to extract from the waste water of a sink and/or dishwasher or washing machine the thermal energy contained therein and supply it to a hot water reservoir 4 fed by fresh water.

Toward that end, a waste water container 1 collecting the waste water and a heat pump are firstly provided, the heat pump being embodied here as a compression heat pump having a compressor 13. In this arrangement the evaporator 2 of the heat pump is in thermal contact with the waste water container 1 and the condenser 3 of the heat pump is in thermal contact with the hot water reservoir 4.

In order to avoid dirt deposits in the waste water container 1, which dirt deposits can collect in particular in the bottom region of the waste water container 1 during the time that heat is being extracted from the waste water, the waste water container 1 is provided with an agitating apparatus.

In the exemplary embodiment the waste water container 1 is implemented as a cylindrical hollow body and is provided both with a waste water inlet 5 and with a waste water outlet 6. The agitating apparatus has a drive shaft 7 running coaxially in the waste water container 1 and having agitating elements 8 arranged thereon. Said agitating elements 8 can be formed as individual agitating blades or else—in a manner not illustrated in greater detail—by a worm. Furthermore, such embodiments are also possible in which the agitating elements 8 form a closure means for the waste water.

A valve 9 is provided at the waste water outlet 6 as a closure means for the waste water, enabling the waste water container 1 to be emptied as soon as the thermal energy stored in the waste water has been extracted to a sufficient extent.

As is apparent from the drawing, the agitating elements 8 are embodied such that either they are in contact with the wall surface of the waste water container 1, which necessitates a certain elasticity on the part of the agitating elements 8, or else they are disposed facing said wall surface with a slight gap.

As can be seen from the drawing, the drive shaft 7 is driven by a small electric motor 10 which—in view of the only small circulation capacity—can be designed for low energy consumption. Said circulation of the waste water not only prevents dirt particles from being deposited, but at the same time the waste water is kept at an even temperature level, with the result that the thermal energy can be extracted more quickly and efficiently via the wall surface of the waste water container 1.

The drive shaft 7 together with the agitating elements 8 and the motor 10 can be embodied as an easily removable structural unit in order in this way to facilitate a nonetheless still occasionally necessary cleaning of the waste water container 1.

The waste water container 1 is arranged inside the device, inclined at an angle with a fall toward the waste water outlet 6, thereby facilitating the conveyance of dirt particles toward the waste water outlet 6.

In order to achieve a preheating of the fresh water being supplied to the hot water reservoir 4, a preliminary heat exchanger 11 for the fresh water is provided on the waste water container 1. Said preliminary heat exchanger 11 is formed by a coiled pipe running in a spiral shape around the housing of the waste water container 1. The coiled pipe of the evaporator 2 is arranged between the individual coils of the coiled pipe of the preliminary heat exchanger 11 in the manner of a common bifilar winding.

The outlet of the preliminary heat exchanger 11 is connected to the inlet of the hot water reservoir 4, said inlet being arranged in the lower region of the hot water reservoir 4 so that the cooler fresh water collects in the lower region of the hot water reservoir 4. The condenser 3 and the hot water outlet, on the other hand, are located in the upper region of the hot water reservoir 4 so that mixing of the inflowing cold fresh water with the hot water that is to be drawn off at the outlet is avoided to the greatest possible extent.

As indicated in the drawing, the waste water container 1, the heat pump and the hot water reservoir 4 are enclosed by a common heat-insulating means 12, as a result of which the entire device furthermore forms a compact structural unit which replaces the hot water boiler normally arranged under a sink. 

1-15. (canceled)
 16. A device for preparing hot water, comprising: a heat pump having an evaporator and a condenser; a waste water container collecting waste water and placed in thermal contact with the evaporator, said waste water container being constructed as a cylindrical hollow body having a waste water inlet and a waste water outlet; a hot water reservoir in thermal contact with the condenser; an agitating apparatus accommodated in the hollow body, said agitating apparatus including a drive shaft running coaxially in the waste water container and agitating elements arranged on the drive shaft; and a valve provided at the waste water outlet to cut a flow of waste water through the waste water outlet.
 17. The device of claim 16 for use in domestic application.
 18. The device of claim 16, wherein the heat pump is a compression heat pump.
 19. The device of claim 16, for use in the recovery of heat from waste water from a sink and/or a dishwasher or washing machine.
 20. The device of claim 16, wherein the agitating elements are constructed in the form of a worm.
 21. The device of claim 16, wherein the agitating elements are structured in a way as to form a closure for waste water.
 22. The device of claim 16, wherein the agitating elements are constructed to contact a wall surface of the waste water container.
 23. The device of claim 16, wherein the agitating elements are constructed at a distance to a facing wall surface of the waste water container to thereby define a gap there between.
 24. The device of claim 16, further comprising a motor to drive the drive shaft.
 25. The device of claim 24, wherein the drive shaft together with the agitating elements and the motor is constructed as a structural unit which is removably connected to the waste water container for cleaning purposes.
 26. The device of claim 16, wherein the waste water container is arranged inclined at an angle with a fall toward the waste water outlet.
 27. The device of claim 16, further comprising a preliminary heat exchanger for fresh water, said preliminary heat exchanger being provided on the waste water container.
 28. The device of claim 27, wherein the preliminary heat exchanger is formed by a coiled pipe running in a spiral shape around a housing of the waste water container.
 29. The device of claim 28, wherein the evaporator has a coiled pipe, said coiled pipe of the preliminary heat exchanger and said coiled pipe of the evaporator being arranged in a manner of a common bifilar winding.
 30. The device of claim 27, wherein the hot water reservoir has an inlet provided in a lower region of the hot water reservoir, said inlet being connected to an outlet of the preliminary heat exchanger.
 31. The device of claim 16, wherein the hot water reservoir has a hot water outlet, said condenser and said hot water outlet being arranged in an upper region of the hot water reservoir.
 32. The device of claim 16, further comprising a common heat insulation enclosing the waste water container, the heat pump and the hot water reservoir. 